The present invention relates to a method for etching an organic/inorganic hybrid film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0), a semiconductor device having an interlayer insulating film made of the organic/inorganic hybrid film, and a fabricating method for such a semiconductor device.
Recent semiconductor integrated circuit devices adopt multilayer interconnection structures to meet requests for size scale-down and higher integration. Conventionally, a silicon oxide (SiO2) film has been used as an interlayer insulating film provided between lower interconnections and upper interconnections. Contact holes are formed through such an interlayer insulating film by plasma etching for connection with lower interconnections when a multilayer interconnection structure is adopted.
Hereinafter, as a first conventional example, an etching method for formation of contact holes through an interlayer insulating film made of a silicon oxide film will be described with reference to FIGS. 22(a) to 22(d).
First, as shown in FIG. 22(a), a lower interconnection 12 made of copper, for example, is formed in an insulating film 11 deposited on a semiconductor substrate 10 by a known method. On the lower interconnection 12, deposited is an etching stopper film 13 made of a silicon nitride (Si3N4) film, for example, that has the function of preventing the lower interconnection 12 from oxidizing during etching and also stopping the etching. An interlayer insulating film 14 made of a silicon oxide (SiO2) film is deposited on the etching stopper film 13. A resist pattern 15 having an opening for formation of a contact hole is then formed on the interlayer insulating film 14. Note that, although illustration is omitted, the sides and the bottom of the lower interconnection 12 are normally coated with barrier metal.
Thereafter, as shown in FIG. 22(b), a contact hole 16 is formed through the interlayer insulating film 14 using the resist pattern 15 as a mask by plasma etching with an etching gas containing fluorine and carbon, such as CF4 gas, C2F6 gas, C3F8 gas, CHF3 gas, C3F8 gas, or C4F8 gas.
As shown in FIG. 22(c), the resist pattern 15 is removed by ashing with oxygen plasma. As shown in FIG. 22(d), the portion of the etching stopper layer 13 exposed in the contact hole 16 is removed.
In recent years, further scale-down and higher integration of multilayer interconnection structures have been demanded, and with realization of this demand, signal delay at interconnections has become greatly influential to the operation speed of a semiconductor integrated circuit.
In order to reduce signal delay at interconnections, it has been proposed to use a film having a low dielectric constant (∈=2 to 3) as the interlayer insulating film. As such a film having a low dielectric constant, known are an organic insulating film containing an organic compound as a main component, a fluorine-containing insulating film made of a fluorine-containing silicon oxide (SiOF), and an organic/inorganic hybrid film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0). Japanese Laid-Open Patent Publication No. 10-125674 proposes an organic/inorganic hybrid film made of a silicon oxide film containing carbon and hydrogen, deposited by feeding hexamethyldisiloxane (HMDSO) as a material gas.
The organic insulating film, of which the composition is similar to that of a resist film, has the following problem. When a resist pattern formed on the organic insulating film is to be removed by ashing with oxygen plasma, the organic insulating film itself is damaged by the oxygen plasma. The fluorine-containing insulating film has the problem that it easily comes off due to its poor adhesion to an underlying film and also it is poor in mechanical strength and heat resistance.
The organic/inorganic hybrid film has a specific dielectric constant considerably smaller than the fluorine-containing insulating film and has a mechanical strength roughly equal to that of the fluorine-containing insulating film. Moreover, the organic/inorganic hybrid film, of which the composition is not similar to that of a resist film, is less damaged by oxygen plasma, and therefore, the resist pattern can be removed by ashing with oxygen plasma.
In consideration of the above, the organic/inorganic hybrid film is promising as an interlayer insulating film having a low specific dielectric constant.
With the recent demand for size scale-down and higher integration of semiconductor integrated circuit devices, also, the diameter of contact holes formed through the interlayer insulating film has become finer and the aspect ratio of the contact holes has become larger. It is difficult to fill such fine contact holes having a large aspect ratio with a conductive material with reliability.
To solve the above problem, Japanese Laid-Open Patent Publication No. 8-191062, for example, proposes a technique in which the diameter of the contact holes is made larger near the opening thereof than near the bottom thereof, to facilitate filling of the contact holes with a conductive material.
Hereinafter, as the second conventional example, the etching method disclosed in Japanese Laid-Open Patent Publication No. 8-191062 will be described with reference to FIGS. 23(a) to 23(d). Note that in FIGS. 23(a) to 23(d), illustration of a lower interconnection is omitted.
First, as shown in FIG. 23(a), a resist pattern 15 having an opening 15a for formation of a contact hole is formed on an interlayer insulating film 14 made of a silicon oxide film deposited on a semiconductor substrate 10.
As shown in FIG. 23(b), the interlayer insulating film 14 is subjected to anisotropic dry etching with an etching gas containing fluorine and carbon using the resist pattern 15 as a mask, to form a contact hole 16 to reach partway in the interlayer insulating film 14.
Isotropic dry etching is then performed for the interlayer insulating film 14 with an etching gas including oxygen gas. By this etching, as shown in FIG. 23(c), an opening 15a of the resist pattern 15 is widened, and with this, the diameter of the contact hole 16 is made larger near the opening thereof, to provide a tapered wall at the opening of the contact hole 16.
As shown in FIG. 23(d), the resist pattern 15 is removed. Although illustration is omitted, by depositing a conductive material on the interlayer insulating film 14, the contact hole 16 is filled with the conductive material with reliability.
(First Problem)
The plasma etching for forming fine contact holes through an organic/inorganic hybrid film is normally performed with an etching gas containing fluorine and carbon, which can cleave Sixe2x80x94O bonds, as in the plasma etching of a silicon oxide film.
However, when the organic/inorganic hybrid film is etched with the same etching gas under the same conditions as those used for etching of the silicon oxide film, the etching rate largely decreases, or in an extreme case, the etching itself stops. The decrease in etching rate causes reduction in throughput. This also causes reduction in the difference between the etching rate of the interlayer insulating film and that of the resist pattern, failing to secure a sufficiently large etching selection ratio.
By adding oxygen gas to the etching gas, the etching rate of the organic/inorganic hybrid film increases. However, this also facilitates etching of the resist pattern 15, and thus the etching selection ratio of the interlayer insulating film 14 to the resist pattern 15 decreases.
The addition of oxygen gas to the etching gas also increases the etching rate of the silicon nitride film constituting the etching stopper film 13. This reduces the etching selection ratio of the interlayer insulating film 14 to the etching stopper film 13.
Therefore, it is not preferable to add oxygen gas to the etching gas.
In view of the above, the first object of the present invention is providing good plasma etching for an organic/inorganic hybrid film.
(Second Problem)
As described above, the etching stopper film 13 made of a silicon nitride film is deposited on the lower interconnection 12 made of a copper film, for example. The specific dielectric constant of the silicon nitride film is about 7, which is significantly large compared with the specific dielectric constant of the organic/inorganic hybrid film.
Having such an etching stopper film, therefore, the reduction in specific dielectric constant between the upper and lower interconnections is not sufficiently attained despite of the formation of the interlayer insulating film 14 made of the organic/inorganic hybrid film in an attempt to reduce the specific dielectric constant.
In view of the above, the second object of the present invention is reducing the specific dielectric constant between the upper and lower interconnections by reducing the specific dielectric constant of the etching stopper film.
(Third Problem)
The second conventional example described above is an etching technique in which the resist film is etched more isotropically to widen the openings of the resist film by adding oxygen gas to the etching gas, to thereby provide contact holes having a tapered opening. However, this technique requires a large amount of etching of the resist film, and therefore it is not possible to increase the thickness of the resist film in an attempt to form contact holes having a large aspect ratio. For this reason, the second conventional example finds difficulty in application to formation of contact holes having a large aspect ratio. In particular, in the case of forming tapered contact holes through the interlayer insulating film made of an organic/inorganic hybrid film, how the etching amount of the resist film should be reduced is a big problem to be solved.
There is also reported a technique in which the contact holes are etched into a tapered shape using an etching gas containing fluorine and carbon without changing the diameter of the openings of the resist film. However, whether or not this technique is applicable to the formation of contact holes through the interlayer insulating film made of an organic/inorganic hybrid film has not been verified.
In view of the above, the third object of the present invention is providing a method in which contact holes having an increased diameter near the opening thereof can be formed through an interlayer insulating film made of an organic/inorganic hybrid film with reliability.
(Fourth Problem)
In recent years, in order to enhance the resolution between light exposed portions and non-exposed portions of a resist film, there has been proposed a technique of forming a resist pattern using a chemical amplification resist material. According to this technique, the polarity (solubility to a developer) is changed in portions of the resist film made of a chemical amplification resist material exposed to an energy beam by the function of acid generated in the exposed portions. The exposed portions or non-exposed portions are then removed with the developer, to form a resist pattern.
The present inventors formed a resist film by applying a chemical amplification resist material to an organic/inorganic hybrid film, and subjected the resist film to pattern light exposure. As a result, it was found that exposed portions of the resist film failed to sufficiently change the polarity presumably due to a reduced amount of acid generated in the exposed portions. Therefore, the resultant resist pattern after removal of the exposed portions or non-exposed portions of the resist film with a developer was faulty in shape.
The present inventors attempted to increase the exposure amount during the pattern light exposure, but failed to sufficiently change the polarity of the exposed portions of the resist film.
The faulty formation of the resist pattern did not occur when a chemical amplification resist film was formed on a silicon oxide film, but was unique to the chemical amplification resist film formed on an organic/inorganic hybrid film. The faulty formation of the resist pattern was confirmed to occur when using a positive chemical amplification resist film, but is presumed to also occur when using a negative chemical amplification resist film.
Hereinafter, a problem occurring in the formation of multilayer interconnections having a dual damascene structure, which uses a chemical amplification resist pattern formed on an organic/inorganic hybrid film, will be described with reference to FIGS. 24(a), 24(b), and 25.
First, as shown in FIG. 24(a), a lower interconnection 22 is formed on an insulating film 21 deposited on a semiconductor substrate 20. An etching stopper film 23 is deposited on the lower interconnection 22, and then an interlayer insulating film 24 made of an organic/inorganic hybrid film is deposited on the etching stopper film 23. Thereafter, a contact hole 25 is formed through the interlayer insulating film 24 by plasma etching using a first resist pattern that is formed on the interlayer insulating film 24 and has an opening for formation of the contact hole.
A chemical amplification resist material is then applied to the resultant interlayer insulating film 24 to form a resist film. The resist film is then subjected to pattern light exposure and development, to form a second resist pattern 26 having an opening for formation of an interconnection groove. At this stage, the resist film partly remains after the above processing, forming a resist film 26a over the top surface of the interlayer insulating film 24 as well as the wall and the bottom of the contact hole 25. The reason why the resist film 26a is formed is considered that acid has been reacted with some reactive group and consumed.
Thereafter, the interlayer insulating film 24 is subjected to plasma etching using the second resist pattern 26 as a mask, to form an interconnection groove 27 in the interlayer insulating film 24 as shown in FIG. 24(b). During this etching, a barrier (inner crown) 28 made of the interlayer insulating film 24 is formed since the resist film 26a on the inner side of the interconnection groove 27 serves as a mask.
After removal of the second resist pattern 26 and the resist film 26a as shown in FIG. 25, the contact hole 25 and the interconnection groove 27 are filled with a conductive material to form a plug and an upper interconnection. At this time, due to the existence of the barrier 28 on the inner side of the interconnection groove 27, the contact resistance between the upper interconnection embedded in the interconnection groove 27 and the plug embedded in the contact hole 25 disadvantageously increases.
In view of the above, the fourth object of the present invention is preventing deactivation of acid in a chemical amplification resist film formed on an organic/inorganic hybrid film, to improve the resolution of the resist film.
(First Resolution Principle)
In order to solve the first problem, the present inventors examined the reason for the reduction of the etching rate when an organic/inorganic hybrid film is subjected to plasma etching with an etching gas containing fluorine and carbon, and found the following.
FIG. 26(a) illustrates a cross-sectional structure of a contact hole 16 formed by dry-etching an interlayer insulating film 14A made of a silicon oxide film with an etching gas containing fluorine and carbon. FIG. 26(b) illustrates a cross-sectional structure of a contact hole 16 formed by dry-etching an interlayer insulating film 14B made of an organic/inorganic hybrid film with an etching gas containing fluorine and carbon.
An etching gas normally contains a carbon component for protection of the resist pattern 15. Therefore, in the dry etching of the interlayer insulating film 14A made of a silicon oxide film, a thin polymer film 17A is deposited on a wall 16a and a bottom 16b of the contact hole 16 as shown in FIG. 26(a). In this process, therefore, both the deposition of the polymer film 17A and the etching proceed competing with each other at the wall 16a and the bottom 16b of the contact hole 16. At the bottom 16b, however, the etching predominates over the deposition. Accordingly, the bottom 16b of the contact hole 16 moves downward, that is, toward the etching stopper film 13.
In the case of dry etching of the interlayer insulating film 14B made of an organic/inorganic hybrid film, a carbon component is contained, not only in the etching gas, but also in the organic/inorganic hybrid film. Therefore, as shown in FIG. 26(b), an etching reaction gas containing a carbon component is generated at the wall 16a and the bottom 16b of the contact hole 16 during the etching of the organic/inorganic hybrid film. As a result, a polymer film 17B having a larger thickness than that shown in FIG. 26(a) is deposited. In this case, also, both the deposition of the polymer film 17B and the etching proceed competing with each other at the bottom 16b of the contact hole 16. However, in this case, progress of the etching is blocked by the carbon component at the bottom 16b as the etching surface of the organic/inorganic hybrid film, together with the polymer film 17B. In the early stage of the etching, that is, when the depth of the contact hole 16 is small, when the introduced amount of the plasma etching species and the plasma energy are sufficient, the etching predominates over the deposition of the polymer film 17B, and therefore the etching proceeds. As the contact hole 16 becomes deeper with the progress of the etching, however, the introduced amount of the plasma etching species and the plasma energy become insufficient, failing to sufficiently remove the carbon component in the organic/inorganic hybrid film. Therefore, a surplus of the carbon component is accumulated on the bottom 16b of the contact hole 16, blocking smooth etching reaction. Since the deposition of the polymer film 17B predominates over the etching, the etching rate gradually decreases, and finally the etching stops.
In consideration of the above, if the etching is carried out while sufficiently removing the polymer film on the bottom of the contact hole and the carbon component existing in the portion of the organic/inorganic hybrid film exposed in the contact hole, the etching should proceed smoothly.
The first and second etching methods according to the present invention are based on the first resolution principle described above.
The first etching method of the present invention is directed to a method for plasma-etching an organic/inorganic hybrid film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0), including the step of: plasma-etching the organic/inorganic hybrid film while eliminating a carbon component from a surface portion of the organic/inorganic hybrid film.
According to the first etching method, the plasma etching is performed while the surface portion of the organic/inorganic hybrid film is reformed by elimination of a carbon component from the surface portion of the organic/inorganic hybrid film. Therefore, in the carbon-eliminated surface portion, in which the amount of the carbon component that facilitates deposition of a polymer film is small, the etching rate improves.
The second etching method of the present invention is directed to a method for plasma-etching an organic/inorganic hybrid film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0), including repeating alternately a first step of eliminating a carbon component from a surface portion of the organic/inorganic hybrid film and a second step of plasma-etching the surface portion from which the carbon component has been eliminated.
According to the second etching method, the first step of eliminating a carbon component from the surface portion of the organic/inorganic hybrid film and the second step of plasma-etching the surface portion from which the carbon component has been eliminated are performed alternately. Therefore, in the carbon-eliminated surface portion, in which the amount of the carbon component that facilitates deposition of a polymer film is small, the etching rate improves.
In the first or second etching method, plasma etching is performed in the state where the carbon component has been eliminated from the surface portion of the organic/inorganic hybrid film, that is, in the state where the amount of the carbon component that blocks cleaving of Sixe2x80x94O bonds and generation of CO2, SiF4, and the like is small in the surface portion of the organic/inorganic hybrid film. Therefore, the etching rate improves. This improves the throughput and also increases the etching selection ratio with respect to the resist pattern.
The second etching method is especially effective in the case that the preferred conditions under which the carbon component is eliminated from the surface portion are different from the preferred conditions under which the surface portion is plasma-etched, such as the case that the preferred gas pressure adopted when the carbon component is eliminated from the surface portion is largely different from the preferred gas pressure adopted when the organic/inorganic hybrid film is plasma-etched.
In the first etching method, the plasma etching is preferably performed with an etching gas containing fluorine, carbon and nitrogen.
In the second etching method, preferably, the first step is performed with a gas containing nitrogen, and the second step is performed with an etching gas containing fluorine and carbon.
In the above case, the gas containing nitrogen may be a mixed gas of hydrogen and nitrogen or ammonia gas.
When a gas containing nitrogen comes into contact with the surface of an organic/inorganic hybrid film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0), xe2x80x9cCxHyxe2x80x9d is chemically changed to highly volatile HCN or CN at the surface of the SiCxHyOz film, and thus the proportion of the carbon component decreases in the surface portion of the organic/inorganic hybrid film (SiCxHyOz film). Therefore, the etching of the organic/inorganic hybrid film proceeds at roughly the same etching rate as that for a silicon oxide film. This mechanism will be described according to reaction formulae as follows.
When a gas containing nitrogen comes into contact with the surface of the organic/inorganic hybrid film represented by SiCxHyOz, chemical reaction represented by Formula 1 or Formula 2 below proceeds. 
That is, in the surface portion of the organic/inorganic hybrid film, the carbon component is eliminated, to provide a reformed film having a composition similar to that of a silicon oxide film.
Thereafter, when an etching gas containing fluorine and carbon comes into contact with the reformed layer of the organic/inorganic hybrid film, the CFx contained in the etching gas reacts with the reformed layer as represented by Formula 3 or Formula 4 below, and thus etching proceeds. 
Thus, xe2x80x9cCxHyxe2x80x9d is removed from the surface portion of the SiCxHyOz film, to form the reformed layer represented by SiHyxe2x88x92xOz or SiHyOz, and the reformed layer is then etched with an etching gas containing fluorine and carbon. In this way, the plasma etching can be performed for the organic/inorganic hybrid film (SiCxHyOz film) at roughly the same etching rate as that for a silicon oxide film (SiO2 film).
The above phenomenon that C or CxHy is removed from the SiCxHyOz film implies that the proportion of oxygen atoms in the film increases. This phenomenon can therefore be considered as oxidation.
The reformation of the surface portion of the SiCxHyOz film is a process of removing the carbon component in the surface portion of the SiCxHyOz film by changing the carbon component to HCN or CN. Therefore, if no hydrogen atoms or only a small amount of hydrogen atoms are contained in the SiCxHyOz film, hydrogen gas may be mixed in the gas for reformation to enable efficient progress of the reformation and thus the etching.
In plasma etching of an inorganic insulating film containing no carbon component at all, such as a SiOF film, there is known an etching method using an etching gas obtained by mixing a nitride such as NH3 in a CF4 gas that is normally used for etching of a silicon oxide film (Japanese Laid-Open Patent Publication No. 9-263050).
The above conventional etching method is based on a technical thought as follows. By mixing a nitride in the etching gas, fluorine radicals (F*) in the plasma of the etching gas are scavenged by hydrogen atoms (H), nitrogen atoms (N), or active species thereof freely existing in the plasma, to thereby enhance the selectivity with respect to a silicon substrate or a resist film. This technical thought in Japanese Laid-Open Patent Publication No. 9-263050 is therefore completely different from the etching method of the present invention in which a gas containing a nitrogen component is used for eliminating a carbon component from the surface portion of an organic/inorganic hybrid film represented by SiCxHyOz. 
(Second Resolution Principle)
The second resolution principle is for solving the second problem described above. This utilizes the mechanism that the etching rate is reduced by the existence of a carbon component contained in an organic/inorganic hybrid film represented by SiCxHyOz. That is, an organic/inorganic hybrid film is used as the etching stopper film, in place of a silicon nitride film conventionally used. More specifically, under the interlayer insulating film made of an organic/inorganic hybrid film, an etching stopper film made of an organic/inorganic hybrid film in which the proportion of the carbon component is large compared with the interlayer insulating film is provided.
In place of the organic/inorganic hybrid film, any of silicon insulating films in which the proportion of the carbon component is large, such as a SiC film and the like, may be used.
The first fabricating method for a semiconductor device of the present invention includes the steps of: depositing an etching stopper film on an interconnection layer formed on a substrate, the etching stopper film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; depositing an interlayer insulating film on the etching stopper film, the interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; and forming a contact hole through the interlayer insulating film by plasma-etching the interlayer insulating film.
The first semiconductor device of the present invention includes: an etching stopper film formed on an interconnection layer formed on a substrate, the etching stopper film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; an interlayer insulating film formed on the etching stopper film, the interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; and a contact hole formed through the interlayer insulating film by plasma etching.
According to the first fabricating method of a semiconductor device and the first semiconductor device, the etching stopper film containing a carbon component in a large proportion compared with the interlayer insulating film is formed under the interlayer insulating film. Therefore, once the plasma etching of the interlayer insulating film is completed, the following phenomenon occurs. The etching stopper film containing a larger amount of a carbon component is more or less etched and generates an etching reaction gas containing a carbon component, which is mixed in the plasma. In addition, a large amount of the carbon component exists in the etching stopper film and on the surface thereof. Therefore, a thick polymer film is deposited on the bottom of the contact holes and this sharply reduces the etching rate of the etching stopper film.
Thus, the etching stopper film made of the second organic/inorganic hybrid film in which the proportion of the carbon component is relatively large serves as the etching stopper film for the interlayer insulating film made of the first organic/inorganic hybrid film in which the proportion of the carbon component is relatively small when the latter is plasma-etched to form a contact hole.
In addition, since the above etching stopper film is made of an insulating film having a low specific dielectric constant, the specific dielectric constant between the lower and upper interconnections can be largely reduced, compared with the case of using a silicon nitride film having a large specific dielectric constant.
In the first fabricating method of a semiconductor device, the plasma etching is performed with an etching gas containing fluorine, carbon and nitrogen.
(Third Resolution Principle)
The third resolution principle is for solving the third problem described above. This utilizes the mechanism that the etching rate is reduced by the existence of a carbon component contained in an organic/inorganic hybrid film represented by SiCxHyOz. Specifically, the mechanism is that with increase in the amount of the carbon component contained in an organic/inorganic hybrid film, the polymer film deposited on the wall of a contact hole is thicker and this reduces the etching rate, and with decrease in the amount of the carbon component contained in the organic/inorganic hybrid film, the polymer film deposited on the wall of the contact hole is thinner and this increases the etching rate. The third resolution principle can be realized by the following first and second schemes.
In the first scheme, the lower part of the interlayer insulating film is made of a first organic/inorganic hybrid film that contains a carbon component in a relatively small proportion, and the upper part of the interlayer insulating film is made of a second organic/inorganic hybrid film that contains a carbon component in a relatively large proportion. Plasma etching is carried out for the upper and lower parts of the interlayer insulating film under the same conditions.
In the second scheme, a fixed proportion of a carbon component is contained in the interlayer insulating film made of an organic/inorganic hybrid film. In the early stage of plasma etching of the interlayer insulating film (etching of the upper part of the interlayer insulating film), the amount of the carbon component eliminated from the wall and the bottom of the contact hole is kept relatively small, while in the late stage of the plasma etching of the interlayer insulating film (etching of the lower part of the interlayer insulating film), the amount of the carbon component eliminated from the wall and the bottom of the contact hole is made relatively large.
The second fabricating method for a semiconductor device of the present invention, which embodies the first scheme of the third resolution principle, includes the steps of: depositing a first interlayer insulating film on an interconnection layer formed on a substrate, the first interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; depositing a second interlayer insulating film on the first interlayer insulating film, the second interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; and plasma-etching the second interlayer insulating film and the first interlayer insulating film sequentially, to form a first opening through the second interlayer insulating film, the diameter of the first opening being smaller toward the bottom end, and a second opening through the first interlayer insulating film, the wall of the second opening being vertical to the bottom surface.
The second semiconductor device of the present invention includes: a first interlayer insulating film deposited on a substrate, the first interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; a second interlayer insulating film deposited on the first interlayer insulating film, the second interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; a first opening formed through the second interlayer insulating film by plasma-etching, the diameter of the first opening being smaller toward the bottom end; and a second opening formed under the first opening through the first interlayer insulating film, the wall of the second opening being vertical to the bottom surface.
According to the second fabricating method for a semiconductor device and the second semiconductor device, the second interlayer insulating film deposited on the first interlayer insulating film contains a larger proportion of the carbon component than the first interlayer insulating film. Therefore, the following phenomenon occurs during the plasma etching of the second interlayer insulating film. Both the deposition of a polymer film and the etching proceeds competing with each other at the bottom of the first opening. In this occasion, however, an etching reaction gas containing a large amount of the carbon component is generated during the etching of the second interlayer insulating film, which facilitates deposition of polymer on the wall and the bottom of the first opening. In addition, the carbon component in the second interlayer insulating film blocks progress of the etching at the bottom, causing reduction in etching rate toward the bottom. Therefore, with the progress of the etching toward the bottom of the first opening, a larger amount of polymer is deposited on the wall of the first opening. As a result, formed is the first opening of which the diameter is smaller toward the bottom.
The first interlayer insulating film contains a smaller proportion of the carbon component than the second interlayer insulating film. Therefore, the following phenomenon occurs during plasma etching of the first interlayer insulating film. Both the deposition of a polymer film and the etching proceeds competing with each other at the bottom of the second opening. In this occasion, only a comparatively small amount of an etching reaction gas is generated from the first interlayer insulating film during the etching thereof, and thus deposition of a polymer film on the wall and the bottom of the second opening is small. This enables a sufficient amount of the carbon component to be eliminated from the first interlayer insulating film at the bottom of the second opening, and thus prevents reduction in etching rate toward the bottom. Therefore, with the progress of the etching toward the bottom of the second opening, only a small amount of polymer is deposited on the wall of the second opening. As a result, formed is the second opening of which the wall is roughly vertical to the bottom face.
In the second fabricating method of a semiconductor device, the plasma etching is preferably performed with an etching gas containing fluorine, carbon and nitrogen.
The third fabricating method for a semiconductor device of the present invention, which embodies the second scheme of the third resolution principle, includes the steps of: depositing an interlayer insulating film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) on a substrate; performing first plasma-etching for the interlayer insulating film while blocking or suppressing a carbon component from being eliminated from a surface portion of the interlayer insulating film, to form a first opening in the interlayer insulating film, the diameter of the first opening being smaller toward the bottom end; and performing second plasma etching for the interlayer insulating film while facilitating elimination of the carbon component from the surface portion of the interlayer insulating film, to form a second opening under the first opening in the interlayer insulating film, the wall of the first opening being vertical to the bottom surface.
According to the third fabricating method for a semiconductor device, in the first plasma etching for the interlayer insulating film, which is performed while blocking or suppressing the carbon component from being eliminated from the surface portion of the interlayer insulating film, the following phenomenon occurs. Both the deposition of a polymer film and the etching proceeds competing with each other at the bottom of the first opening. In this occasion, however, since elimination of the carbon component from the interlayer insulating film is blocked or reduced, progress of the etching is impeded, and thus the etching rate decreases toward the bottom. Therefore, with the progress of the etching toward the bottom, a larger amount of polymer is deposited on the wall. As a result, the first opening of which the diameter is smaller toward the bottom is formed in the upper part of the interlayer insulating film.
In the second plasma etching for the interlayer insulating film, which is performed while facilitating elimination of the carbon component from the surface portion of the interlayer insulating film, the following phenomenon occurs. Both the deposition of a polymer film and the etching proceeds competing with each other at the bottom of the second opening. In this occasion, since the carbon component is sufficiently eliminated from the surface of the interlayer insulating film, the etching rate does not decrease with progress of the etching toward the bottom. Therefore, only a small amount of polymer is deposited on the wall in comparison with the progress of the etching toward the bottom. As a result, the second opening of which the wall is vertical to the bottom face is formed in the lower part of the interlayer insulating film.
In the third fabricating method for a semiconductor device, preferably, the first plasma etching is performed with a first etching gas containing fluorine, carbon and nitrogen in which the proportion of nitrogen is relatively small, and the second plasma etching is performed with a second etching gas containing fluorine, carbon and nitrogen in which the proportion of nitrogen is relatively large.
(Fourth Resolution Principle)
As described above, the phenomenon that acid generated in the exposed portions of the resist film is deactivated is unique to the chemical amplification resist film formed on an organic/inorganic hybrid film, and does not occur in the chemical amplification resist film formed on a silicon oxide film. It is not possible to prevent this acid deactivation by increasing the exposure of an energy beam emitted to the resist film. From these facts and others, the acid deactivation is presumed to occur as a result of reaction of acid (H+) generated in the exposed portions with a reactive group contained in the organic/inorganic hybrid film.
In the fourth resolution principle, therefore, a silicon oxide film is interposed between the organic/inorganic hybrid film and the chemical amplification resist film for blocking the reaction of acid generated in the exposed portions with a reactive group contained in the organic/inorganic hybrid film.
The fourth fabricating method for a semiconductor device of the present invention includes the steps of: depositing an interlayer insulating film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) on a substrate; forming a silicon oxide film containing no carbon component on the top surface or a surface portion of the interlayer insulating film; forming a resist film made of a chemical amplification resist material on the silicon oxide film; and subjecting the resist film to pattern exposure and development to form a resist pattern made of the resist film.
According to the fourth fabricating method for a semiconductor device, the silicon oxide film containing no reaction group exists between the interlayer insulating film and the resist film made of the chemical amplification resist material. Therefore, acid generated in exposed portions of the resist film is prevented from reacting with the carbon component contained in the interlayer insulating film, and thus prevented from deactivation. This ensures the polarity (solubility to a developer) of the exposed portions of the resist film, and thus after removal of the exposed portions or non-exposed portions of the resist film with a developer, the resultant resist pattern is good in shape.
In the fourth fabricating method for a semiconductor device, the silicon oxide film may be formed by eliminating a carbon component from the surface portion of the interlayer insulating film.
The fifth fabricating method for a semiconductor device of the present invention includes the steps of: depositing an etching stopper film on an interconnection layer formed on a substrate, and then depositing an interlayer insulating film represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) on the etching stopper film; forming a contact hole through the interlayer insulating film; forming a resist pattern made of a chemical amplification resist material, the resist pattern having an opening for formation of an interconnection groove, and also forming a protection film made of the chemical amplification resist material on the bottom of the contact hole for protecting the etching stopper film; and plasma-etching the interlayer insulating film using the resist pattern, to form the interconnection groove in the interlayer insulating film.
According to the fifth fabricating method for a semiconductor device, the protection film made of a chemical amplification resist material is formed on the bottom of the contact hole for protecting the etching stopper film. With the protection film formed in the contact hole, the interlayer insulating film is plasma-etched to form an interconnection groove therein. Therefore, the portion of the etching stopper film exposed in the contact hole is prevented from being exposed to the plasma for formation of the interconnection groove and thus is damaged less easily. Using this method, the etching stopper film can be made thin and still can protect the interconnection layer from being still can protect the interconnection layer from being exposed to the plasma. It is therefore possible to avoid damaging of the surface of the interconnection layer or formation of a naturally oxidized film on the surface of the interconnection layer.
The sixth fabricating method for a semiconductor device of the present invention, which corresponds to application of the first and second resolution principles to a fabrication process of a semiconductor device, includes the steps of: depositing an etching stopper film on an interconnection layer formed on a substrate, the etching stopper film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; depositing an interlayer insulating film on the etching stopper film, the interlayer insulating film being represented by SiCxHyOz (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; depositing a CMP stopper film on the interlayer insulating film; forming a resist pattern having an opening for formation of a contact hole on the CMP stopper film; transferring the opening of the resist pattern to the CMP stopper film, and then plasma-etching the interlayer insulating film while eliminating a carbon component from a surface portion of the interlayer insulating film, to form a contact hole through the interlayer insulating film; after removal of the resist pattern, depositing a conductive film resist pattern, depositing a conductive film on the CMP stopper film to fill the contact hole with the conductive film; and removing a portion of the conductive film exposed on the CMP stopper film by CMP, to form a plug made of the conductive film.
According to the sixth fabricating method for a semiconductor device, a contact hole is formed through the interlayer insulating film by performing plasma etching while eliminating the carbon component from the surface portion of the interlayer insulating film. Formation of a polymer film is reduced on the surface portion from which the carbon component has been eliminated. Therefore, the etching rate does not decrease, and thus the contact hole can be formed through the interlayer insulating film with reliability.
The etching stopper film containing a carbon component in a large proportion compared with the interlayer insulating film is formed under the interlayer insulating film. Therefore, once the plasma etching of the interlayer insulating film is completed, the following phenomenon occurs. The etching stopper film containing a larger amount of a carbon component is more or less etched and generates an etching reaction gas containing a carbon component, which is mixed in the plasma. In addition, a large amount of the carbon component exists in the etching stopper film and on the surface thereof. Therefore, a thick polymer film is deposited on the bottom of the contact hole, and this sharply reduces the etching rate of the etching stopper film. Thus, the etching stopper film in which the proportion of the carbon component is relatively large serves as the etching stopper film when the interlayer insulating film is plasma-etched to form a contact hole.
In addition, the etching stopper film is made of an insulating film having a low specific dielectric constant, and thus enables large reduction in the specific dielectric constant between the lower and upper interconnections, compared with a silicon nitride film having a large specific dielectric constant.
Moreover, the CMP stopper film is interposed between the interlayer insulating film and the conductive film for formation of the plug. The interlayer insulating film is therefore protected from being subjected to CMP when the portion of the conductive film exposed on the CMP stopper film is removed by CMP. Therefore, the interlayer insulating film is prevented from being damaged even though it is made of an organic/inorganic hybrid film that is susceptible to CMP.
The seventh fabricating method for a semiconductor device of the present invention, which corresponds to application of the first and second resolution principles to a fabrication process of multilayer interconnections having a dual structure, includes the steps of: depositing an etching stopper film on a lower interconnection formed on a substrate, the etching stopper film being represented by SiCXHYOZ (x greater than 0, yxe2x89xa70, zxe2x89xa70) in which the proportion of carbon atoms with respect to silicon atoms is relatively large; depositing an interlayer insulating film on the etching stopper film, the interlayer insulating film being represented by SiCXHYOZ (x greater than 0, yxe2x89xa70, z greater than 0) in which the proportion of carbon atoms with respect to silicon atoms is relatively small; depositing a CMP stopper film on the interlayer insulating film; forming a first resist pattern having an opening for formation of a contact hole on the CMP stopper film; transferring the opening of the first resist pattern to the CMP stopper film, and then plasma-etching the interlayer insulating film while eliminating a carbon component from a surface portion of the interlayer insulating film, to form a contact hole through the interlayer insulating film; after removal of the first resist pattern, forming a second resist pattern having an opening for formation of an interconnection groove on the CMP stopper film; transferring the opening of the second resist pattern to the CMP stopper film, and then plasma-etching the interlayer insulating film while eliminating a carbon component from a surface portion of the interlayer insulating film, to form an interconnection groove in the interlayer insulating film; depositing a conductive film on the CMP stopper film to fill the contact hole and the interconnection groove with the conductive film; and removing a portion of the conductive film exposed on the CMP stopper film by CMP, to form a plug and an upper interconnection made of the conductive film.
According to the seventh fabricating method for a semiconductor device, as in the sixth fabricating method, a contact hole is formed through the interlayer insulating film by performing plasma etching while eliminating the carbon component from the surface portion of the interlayer insulating film. Therefore, the etching rate does not decrease, and thus the contact hole and the interconnection groove can be formed in the interlayer insulating film with reliability.
The etching stopper film in which the proportion of the carbon component is relatively large compared with the interlayer insulating film serves as the etching stopper film when the interlayer insulating film is plasma-etched to form a contact hole and an interconnection groove.
In addition, the etching stopper film is made of an insulating film having a low specific dielectric constant, and thus enables large reduction in the specific dielectric constant between the lower and upper interconnection, compared with a silicon nitride film having a large specific dielectric constant.
Moreover, the CMP stopper film is interposed between the interlayer insulating film and the conductive film for formation of the plug and the upper interconnection. The interlayer insulating film is therefore protected from being subjected to CMP when the portion of the conductive film exposed on the CMP stopper film is removed by CMP. Therefore, the interlayer insulating film is prevented from being damaged even though it is made of an organic/inorganic hybrid film that is susceptible to CMP.
Thus, it is ensured to reduce the specific dielectric constant between the lower and upper interconnections in multilayer interconnections having a dual damascene structure.